Bearings or half shafts or what?

Trying to eliminate a moaning noise that increases with speed (not RPM) on a 190E 2.6L 5-Sp with 249,000 miles on it. Noise seems to come from the rear, regardless of in gear or in neutral - thus it is a function of MPH. A used differential was installed recently, so I don't think that is the problem (the noise was there before the used diff. was installed). New flex discs and driveshaft center bearing installed, too. If it is the rear bearings, would they make a moan noise or would it be a higher pitched noise (like a chirp that you get when the front bearings are bad)? Could it be half shafts? But I thought when half shafts go bad, they make a Click/Clack noise. Any and all advice is welcome. Thank you.

[sbourg]

I would check tires first, since it's easy and they can make this noise. Swap front/rear. Bearings could be the cause, or rear end. I doubt the axles.

Steve

Good thought since the noise is very much like noisy snow tires. The other week-end I swapped the mounted snows with my summer street wheels/tires. I hoped that the noise was just the snow tires. It wasn't. The noise was still there after the switch.